A known frictional propulsion device for an omni-directional vehicle comprises a main wheel including an annular core member and a plurality of driven rollers (free rollers) fitted on the annular core such that each driven roller may be freely rotatable around the tangential direction of the annular core member at the corresponding position, and a pair of drive disks provided on either side of the main wheel each including a disk member and a plurality of drive rollers (free rollers) arranged along the outer periphery of the disk member and engaging the driven rollers of the main wheel so as to be each rotatable around a rotational center line at an angle to both the lateral direction and the radial direction. See JP2011-63214A and JP2011-63215A, for instance.
In such a structure, it is important that the structure for supporting the drive rollers (free rollers) on each drive disk is mechanically stable, compact and economical. In the structure disclosed in JP2011-63214A, each drive disk is provided with a plurality of slots along the outer periphery thereof to rotatably support the respective drive rollers (free rollers). Each drive roller is received in the corresponding slot and rotatably supported via a pivot shaft so as to be rotatable within the slot.
In the structure disclosed in JP2011-63215A, each drive roller is rotatably supported by a bracket, and the bracket is in turn fitted into a corresponding groove formed in the drive disk. An annular side plate is attached to the drive disk to firmly retain each bracket in the groove.
According to the structure disclosed in JP2011-63214A, a large number of slots have to be formed in the disk member by milling, and owing to the three-dimensionally slanted configuration of each slot, a highly complex milling process is required, and this increases the manufacturing cost. Furthermore, because each drive roller is provided with a bearing, the assembling of the drive rollers requires considerable work hours. For the details of the assembly work, reference should be made to JP2011-63215A.
According to the structure disclosed in JP2011-63215A, a large number of grooves have to be formed in the disk member by milling, and this also involves a highly complex milling process. Furthermore, each bracket is retained by the corresponding groove in the manner of a cantilever so that it is difficult to achieve an adequate mechanical strength without increasing the overall size.
Therefore, there is a need for a drive disk design which is mechanically stable, compact and economical.